digestive system Flashcards
2.30 where is bile produced?
the liver
2.30 where is bile stored?
the gall bladder
2.27 describe the structure & function of the human alimentary canal - what order does the food go through each organ?
- mouth
- oesophagus
- stomach
- duodenum (small intestine)
- ileum (small intestine)
- colon (large intestine)
- rectum (large intestine)
- anus
2.27 describe structure & function of mouth/what happens in the mouth?
- ingestion takes place here
- digestion begins here - mechanical & chemical
- swallowing, flap called epiglottis which blocks food from entering the trachea
what mechanical digestion happens in the mouth?
food broken up into smaller pieces in mouth by chewing. this inc SA for enzymes & also prevents discomfort when swallowing
what chemical digestion happens in the mouth?
saliva released into mouth by salivary glands - makes food easier to swallow, & also contains enzyme amylase. amylase works best at neutral pH, so is denatured when it reaches stomach & stops working
2.27 describe the structure and function of the oesophagus
- long tube that connects mouth to stomach
- food pushed down by peristalsis
- 2 sets of muscles push food down oesophagus: the circular muscles contract behind the bolus pushing it along, & when the longitudinal muscles contract they make oesophagus wider
2.27 describe the structure and function of the stomach
- gastric glands in stomach wall secrete enzyme pepsin, which begins process of digesting proteins into peptides (shorter chains of amino acids)
- contraction of stomach wall causes mixing of contents of stomach, maximising contact between enzymes & food
- pepsin’s optimum conditions are acidic pH - conditions in stomach acidic due to release of HCl by gastric glands
- HCl has very low pH, kills many bacteria & fungi which may be present in food we eat
2.27 describe the structure and function of the small intestine (duodenum)
- duodenum final site of chemical digestion
- pancreas makes several enzymes & secretes them into duodenum: trypsin, amylase & lipase
- duodenum wall also contains glands which make enzymes & secretes them into the duodenum: maltase & peptidase
- duodenum also contains bile, produced by liver & stored in gall bladder, then released into duodenum through bile duct
2.27 describe the structure and function of the pancreas
- pancreas makes several enzymes & secretes them into duodenum: trypsin, amylase & lipase
2.31 what is the role of bile?
- neutralises stomach acid - enzymes in duodenum work best at pH 7-8
- emulsifies lipids - breaks large droplets into smaller droplets, inc SA for lipase to digest fats
2.27 describe the structure and function of the small intestine (ileum)
- once food entered ileum digestion over and absorption begins
- ileum has many folds & covered in finger like projections called villi
- it’s through these that small soluble molecules absorbed
- some absorbed by diffusion but some e.g. glucose also absorbed by active transport
- rate of diffusion inc by ileum’s adaptations
2.32 how is the small intestine adapted for absorption?
rate of diffusion in ileum inc by it having:
- large SA: folding of ileum, villi and microvilli all inc SA
- short diffusion distance: villi walls are one cell thick
- high conc. gradient: provided by capillary network and lacteals removing absorbed molecules
2.27 describe the structure and function of the large intestine (colon & rectum)
- colon site for all reabsorption of water
- faeces then stored in rectum & egested from anus
what’s the definition for digestion?
the breakdown of large insoluble molecules into small soluble molecules
what is ingestion?
taking food in through the mouth & swallowing
what is absorption?
the movement of small soluble molecules out of the gut & into the blood by diffusion and AT
what is egestion?
passing out undigested food through the anus
definition of assimilation?
building larger biological molecules from the small soluble molecules, in all cells
2.25 identify the sources and describe the functions of carbohydrate
food source - bread, potatoes, rice, cereals, fruit
function - fuel for respiration
2.25 identify the sources and describe the functions of proteins
food source - meat, eggs, fish, quinoa, quorn
function - growth & repair of cells and tissues, fuel for respiration
2.25 identify the sources and describe the functions of lipid (fats and oils)
food source - butter, cooking oil, cream, avocados
function - store of energy (thermal & electrical), insulation, fuel for respiration
2.26 how do energy requirements vary with activity levels, age and pregnancy?
activity levels - will need more energy
age - teenagers need more energy for growth
pregnancy - need more energy
2.25 identify the sources and describe the functions of vitamin A
function - making a chemical in the retina & also protects the surface of the eye
food source - fish liver oil, liver, butter, carrots
effect of deficiency - night blindness & damaged cornea
2.25 identify the sources and describe the functions of vitamin C
function - needed for cells & tissues to stick together
effect of deficiency - scurvy
food source - fresh fruit & vegetables, orange
2.25 identify the sources and describe the functions of vitamin D
function - needed to absorb calcium & phosphate ions from food
effect of deficiency - rickets, caused by weak bones
food source - dairy products, oily fish
2.25 identify the sources and describe the functions of the mineral ion calcium
function - needed to form bones & teeth
food source - milk & dairy products, fish, fresh vegetables
deficiency disease - rickets
2.25 identify the sources and describe the functions of the mineral ion iron
function - forms the part of haemoglobin which binds to oxygen
food source - red meat, liver, spinach
deficiency disease - anaemia
2.25 identify the sources and describe the functions of water
- essential solvent (allows things to be dissolved into it)
- used to transport components of blood
- crucial for temp regulations (e.g. sweating)
2.25 identify the sources and describe the functions of dietary fibre
- plant material that you cant digest, mainly chemical called cellulose
- helps movement of food through intestine, prevents constipation & bowel cancer
2.28 how is food moved through the gut?
by peristalsis
2.24 what should a balanced diet include?
appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre
2.33B practical: investigate the energy content in a food sample
- measure 25cm³ water into a boiling tube
- record starting temp
- measure mass of foodstuff
- put sample of foodstuff onto mounted needle & light it on fire w Bunsen burner
- hold under boiling tube of water to heat it
- if food stops burning, needs to be relit until will no longer burn
- measure finishing temp or water & calculate temp change
- energy content calculated using: energy transferred per gram of food (J) = (mass of water (g) x temp change x 4.2)/mass of food sample (g)
2.33B what’s the equation to find the energy content in a food sample?
energy transferred per gram of food (J) = (mass of water (g) x temp change x 4.2)/mass of food sample (g)
what happens to amylase when it reaches the stomach?
amylase works best at neutral pH, so is denatured when it reaches stomach & stops working
2.29 what enzyme is in saliva?
amylase
2.29 what are the 3 main types of digestive enzyme?
carbohydrases, proteases, and lipases
2.29 where is amylase (a carbohydrase) made in the digestive system?
the salivary glands, the pancreas, & the small intestine
2.29 where are proteases made in the digestive system?
- pepsin made in stomach which breaks down proteins into smaller polypeptide chains/peptides
- trypsin made in the pancreas & released in the duodenum break the proteins to peptides
- peptidase in the lining of duodenum break peptides into amino acids
2.29 where are lipases made in the digestive system?
lipase made by the pancreas & secreted into the duodenum
